Electric power assisted bicycle

Abstract: The present invention relates to an electrically power assisted bicycle wherein the electrical power assist components are comprised of an electric motor (43) and transmission as one unit and a battery (46) as another unit. The electrical motor (43) and the electrical battery (46) are disposed substantially weight-balanced with respect to the crank axis of a manually operated crankshaft. In this way, a low center of gravity and improved manoeuvrability of the bicycle is obtained.

Description: This invention relates to an electrically power assisted bicycle comprising a frame, a front wheel to be dirigibly supported by said frame, a rear wheel journalled for rotation by said frame, a seat carried by said frame for accommodating a rider, a pedal assembly journalled by the frame for rotation about a transverse crank axis for operation by the rider seated on said seat, a drive means coupling said pedal assembly to said rear wheel for manually driving said rear wheel, and an electrical power assist mechanism for transmitting a driving force to said rear wheel through said drive means and comprising an electrical motor and an electrical battery for providing electrical power to said electrical motor. Such an electric power assisted bicycle is known from GB-A-2 083 423 according to which the electric motor is disposed in the frame member or at least coaxially with this frame member. Thereby, said frame member extends generally vertical in use and, in addition, this frame member or the respective axis thereof extends through the output shaft (crank axis) so that this motor has still no lever arm with respect to the crank axis. Therefore, this electric motor cannot be balanced by any of the other parts, especially not by the battery. Moreover, the center of gravity of the battery has a large lever arm and therefore imparts a relatively large moment of rotation about this crank axis. Moreover, electrically power assisted bicycles of the type shown in European Patent Applications 0 559 231, 0 590 674, 0 517 224 and 0 569 954, have a number of advantages. In the construction shown in each of those applications and the aforenoted patent, the bicycle is provided with a conventional pedal mechanism operated by the rider. In addition, there is provided an electric motor powered by a battery and controller arrangement for assisting the operator effort in response to the pedal input force so as to make the riding of the bicycle easier while at the same time maintaining its ability to provide exercise for the rider. In the arrangements shown in those applications, the motor and its driving transmission are disposed in a generally vertically orientation either aligned with or beneath the seat pillar. The battery and controller are disposed in a somewhat horizontally extending position along the main frame member that extends from the head pipe downwardly toward the pedal mechanism. Although this arrangement has a number of advantages, it tends to move the center of gravity of the bicycle generally forwardly of the crank mechanism and also somewhat elevates the center or gravity. Of course, by positioning these mechanisms below the crank axis, the aforenoted problems could be avoided but this would then substantially restrict the ground clearance for the bicycle. Accordingly it is the objective of the present invention to provide an improved electrical power assisted bicycle of the type as indicated above, having a low centre of gravity, providing sufficient ground clearance and having improved manoeuvrability properties. Moreover, the new bicycle should allow a facilitated servicing and maintenance of the components of the electrical power assist system. According to the present invention, the afore-mentioned objective is solved for an electrically power assisted bicycle as indicated above in that said electrical motor and said electrical battery are disposed substantially weight-balanced with respect to the crank axis. In this way heavy components are disposed in a well-balanced manner around the crankshaft, so that the centre of gravity of the bicycle body is near to the centre of the main frame profile. Accordingly, an improved riding feeling is acquired and the bicycle has sufficient ground clearance which also adds to the riding comfort. Preferred embodiments of the present invention are laid down in the further subclaims. In the following, the present invention is explained in greater detail by means of a preferred embodiment thereof in conjunction with the accompanying drawings therein: Figure 1 is a side elevational view of an electric motor assisted bicycle constructed in accordance with an embodiment of the invention. Figure 2 is an enlarged top plan view looking generally in the direction of the arrow 2 in Figure 1 and shows the relationship of the pedal mechanism, the driving electric motor and transmission, and the battery case. Figure 3 is a schematic view showing the various elements of the drive for the rear wheel and the control therefor. Figure 4 is an enlarged side elevational view, looking generally in the direction of the arrow 4 in Figure 2, with portions broken away so as to show the torque sensing mechanism and speed sensor. Figure 5 is a partially exploded view showing the electric motor and transmission arrangement of the prior art type of construction. Figure 6 is an enlarged cross-sectional view taken along the lines 6-6 of Figure 4. Figure 7 is a further enlarged cross-sectional view taken along the lines 7-7 of Figure 6. Figure 8 is a cross-sectional view taken along the line 8-8 of Figure 6. Figure 9 is an enlarged perspective view, with a portion broken away, of the one-way clutch mechanism shown in Figure 7. Figure 10 is a partial side elevational view, in part similar to Figure 7 and shows a prior art type of construction, with portions broken away. Figure 11 is a cross-sectional view taken along the line 11-11 of Figure 10. Figure 12 is an enlarged side elevational view showing the interrelationship between the seat, seat pillar and battery case and shows the seat in an intermediate position and in a battery access position in phantom and solid lines, respectively. Detailed Description of the Preferred Embodiments of the Invention Referring now in detail to the drawings and initially primarily to Figures 1 and 2, an electric power assisted bicycle constructed in accordance with an embodiment of this invention is identified generally by the reference numeral 21. The bicycle 21 is comprised of a frame assembly, indicated generally by the reference numeral 22, which is comprised of a head pipe 23 that dirigibly journals a front wheel 24 by means of a fork assembly 25. A handlebar 26 is affixed to the upper end of the fork assembly 25 in a well known manner for steering of the front wheel 24. The frame assembly 22 further includes a downwardly inclined main frame tube 27 that extends rearwardly and downwardly from the head pipe 23 and which terminates at its lower end in a connecting piece 28. The connecting piece 28 has affixed to it a seat pillar 29 upon which a saddle-type seat 31 is connected in a manner which will be described. The connecting piece 28 is also connected to the upper end of a transmission and pedal support case 32 which journals a crankshaft 33 in a manner which will be described from which a pair of crank arms 34 extend on opposite sides of the case 32. Pedals 35 are journalled at the outer ends of the crank arms 34 in a known manner. The axis of rotation of the crankshaft 33 is disposed generally transversely of the frame assembly 22. A rear wheel 36 is journalled for rotation from the frame assembly 22 by means of a rear arm or yoke 37 that is connected to a bracket 38 which is suitable affixed to the case 32 and a pair of back stays 39 which extend from the flattened ends 41 of the yoke 37 and which are connected at their upper ends to the seat pillar 29. The crank assembly and specifically the crankshaft 33 drives a sprocket, to be described, which in turn drives the rear wheel 36 through a chain 42. The chain 42 is encompassed by a chain guard 43' that is affixed to the frame assembly 22 and one of the back stays 39 at one side of the bicycle 21. In addition to the manual drive for the rear wheel 36, the bicycle 21 is also provided with an electric power assist mechanism which includes an electric motor 43 which is mounted in a manner to be described beneath the main frame tube 27 and thus maintains a low center of gravity. The electric motor 43 receives electrical power from a pair of batteries 44 that are contained within a battery case 45 that is mounted, in a manner to be described, to the rear of and extending parallel to the seat pillar 29. The seat 31 is movable, in a manner which will be described, so as to access the batteries 44 for replacement and/or service. The batteries 44 supply power to the electric motor 43 through a controller, indicated generally by the reference numeral 46, and which is mounted on the underside of the main frame tube 27 forwardly and above the electric motor 43. The controller 46 is powered by the batteries 44 through a main switch 47 that is affixed to the underside of the main tube 27 adjacent the head pipe 23. Accordingly, the main switch 47, the controller 46 and the electrical motor 43 are disposed in a row along the main frame tube 27 inclined from front to rear with the controller 46 and the main switch 47 being forward of the electrical motor 43. The main switch 47 is constituted such that when a key (not shown) is inserted and turned clockwise from the neutral position for example in Figure 1, the controller 46 is electrically connected to the batteries 44 and when turned counterclockwise, a locking device for the battery case 45 is released. It should be roadily apparent that the forward positioning of the electric motor 43 and controller 46 relative to the axis of the crankshaft 33 and the rearward positioning of the batteries 44 and battery case 45 relative to this axis provides substantially equal fore and aft balance so as to maintain the stability of the bicycle 21. Also, the components are mounted relatively low so as to maintain a low center of gravity while not being so low as to provide reduced ground clearance. The electric motor 43 and controller 46 are enclosed partially within a case assembly 48 that is comprised of an upper member 49 and a lower member 51 which are affixed to each other in any known manner. These members are provided with an opening through which a portion of the controller 46 extends, as indicated by the bracket 52 in Figure 1 so as to permit cooling air flow over components of the controller 46 which should be maintained at relatively low temperatures. A sprocket 53 which is driven from either the crankshaft 33 or electric motor 43 in a manner to be described appears in Figure 2 and drives the aforenoted chain 42 for driving the rear wheel 36. Before describing this driving mechanism in detail by reference to Figures 4 and 6-9, the driving system will be described by reference to Figure 3 which shows the various components schematically. As may be seen in Figure 3, the electrical motor 43 is secured to one end of the case 32 so that a motor axis extends at right angles to the crankshaft 33 and the manual pedal power exerted by the operator seated on the seat 31 on the pedals 35 and crank arms 34 is transmitted through a one-way clutch, indicated schematically at 54 to the sprocket 53 and chain 42. The chain 42 is, in turn, drivably coupled to the rear wheel 36 by means of a free-wheeling mechanism, shown schematically at 55, which may also comprise a one-way clutch. In a similar manner, the electric motor 43 drives a planetary transmission or other speed-reducing transmission, shown schematically at 56, which in turn, also drives the sprocket 53 through a one-way clutch, indicated schematically at 57. In other words, between a motor output shaft 63 and the crankshaft 33 the planetary gear transmission 56 and a planetary roller type transmission as explained hereinafter are disposed. In the electrical assist power unit all the rotary parts are arranged coaxially with the diameter of the crankshaft 33 being smaller than that of the sprocket 53 to secure sufficient ground clearance. The controller 46 operates the electric motor 43 in accordance with a system to provide power assist for driving the rear wheel 36 with the amount of power assist being determined, at least in part, by the force exerted by the operator on the pedals 35 The strategy described in any of the aforenoted copending European patent applications, may be employed. Basically, this arrangement incorporates a speed sensor, indicated generally at 58 and shown in block form in this figure, and a torque sensor, indicated generally at 59, and also shown in block form. Because of the fact that the operator operates the mechanism through a pedal and crank mechanism, the actual torque output will vary depending upon the angular relationship of the crank arms 34 relative to the axis of the crankshaft 33, as is well known and is as described in the aforenoted copending applications. Before describing the actual physical embodiment of the drive for the rear wheel 36, one of the problems attendant with certain types of prior art constructions will be described by particular reference to Figure 5, which shows how an electric motor, indicated generally by the reference numeral 201, is coupled to a speed reducer transmission, indicated generally by the reference numeral 202, which is, in turn, then connected to an outer housing 203 of the driven element, such as the housing assembly or pedal support case 32 in this embodiment. With the prior art type of constructions, the electric motor 201 is provided with an outer housing 204 having a front face 205 through which a splined output shaft 206 extends. The output shaft 206 of the electric motor 201 is coupled to an input shaft (not shown) of the transmission 202 so as to drive an output shaft 207 that extends through a rear face 208 of its outer housing 209. The outer housing 209 is provided with a recess 211 into which the front face 205 of the electric motor 201 must be assembled. Hence, there is a problem of alignment of the output shaft 206 with the transmission shaft, as well as of the housings 204 and 209. In addition, the shaft 207 must be connected to a shaft (not shown) in the final drive outer housing 203, and the transmission outer housing 209 is received in a recess 212 of this housing 203. As a result, it should be seen that the construction of the prior art provides not only a rather elongated construction due to the assembly of several housings and components with each other, but also presents a problem of aligning a number of shafts and supporting housings with each other. One feature of the construction avoids this arrangement, and this will now be described in detail by particular reference to Figures 4, 6 and 8, wherein the electric motor 43 and its integral speed reduction transmission is shown in more detail. The electric motor 43 has an outer housing 61 which, in turn, has a rear face 62 through which the electric motor output shaft 63 extends. The transmission 56, shown schematically in Figure 4, is illustrated in detail in Figures 6 and 8, and includes a plurality of planetary frictional elements 64 that are journalled on carrier shaft 65 by intermediate antifriction bearings 66. These planetary frictional elements 64 are held in tight frictional engagement with the outer periphery of the electric motor output shaft 63 upon assembly in a manner which will be described. As a result, there will be established a driving relationship between the motor output shaft 63 and the planetary frictional elements 64. The planetary frictional elements 64 are also engaged within a cylindrical interior of a fixed frictional orbit ring member 67 that has a pair of end plates 68 and 69 and which are affixed to the motor rear face 62 by a plurality of threaded fasteners 71. It is to be understood in actual assembly the orbit element or ring member 67 and end plates 68 and 69 are affixed to the electric motor outer housing 61 before its assembly onto the remainder of the construction, which will be described. The pedal support case or housing 32 is made up of a first member 72 to which a cover plate 73 is affixed. The housing member 72 has a generally cylindrical portion that encircles the orbit ring member 67 and also which encircles a carrier element 74 which has a plurality of bores 75 for receiving the carrier pins 65 on which the planetary elements 64 rotate. A ball-type thrust bearing 76 is loaded between the end of the motor output shaft 63 and the front face of the carrier element 74 so as to provide axial alignment. A pinion shaft 77 is rotatably journalled in the housing member 72 by means of a pair of ball bearings 78 and engages a thrust bearing 79 which, in turn, engages the back face of the carrier element 74. A one-way clutch 81 is interposed between the inner periphery of the carrier member 74 and the pinion shaft 77. The one-way clutch 81 is of a type which permits the insertion of the pinion shaft 77 into it in an axial direction without interference, but which, when assembled, permits the drive to be transmitted from the carrier member 74 to the pinion shaft 77, but does not permit the pinion shaft 77 to drive the carrier member 74. Any known type of one-way clutch may be employed, but one embodying roller-type clutching elements will permit the ease of assembly. By using the frictional planetary transmission 56 as thus far described, it is possible to ensure that the elements can be easily assembled and positioned. This can be done by first fixing the orbit ring member 67 and end plates 68 and 69 to the end of the motor outer housing 61 with the frictional planetary elements 64 positioned between them. The carrier pins 65 can then be inserted into the bearings 66 and frictional planetary elements 64 along with the supporting carrier elements 74. This is done after the assemblage comprised of the end plates 68 and 69, orbit ring member 67 and frictional planetary elements 64 are affixed to the motor outer housing 61 by threaded fasteners 71. This arrangement in essence forms a type of force fit. The outer surface of the motor output shaft 63 will thus form the location of the various elements relative to each other. Subsequently, the electric motor 43 and thus assembled frictional planetary transmission 56 can be thus slipped over the pinion shaft 77 so as to complete the final assembly, and this assembly can be bolted together by means of bolts 82 (Figure 4). The area of the housing member 72 rearwardly of the portion where the carrier element 74 and bearing 78 is positioned is provided with a further cavity that receives, among other things, the crankshaft 33 of the pedal assembly. This crankshaft 33 is journalled for rotation within this cavity with the ends extending outwardly therefrom for connection to the crank arms 34 in a manner which will be described. The pinion shaft 77 is formed with an integral pinion gear which meshes with a ring gear 83. The ring gear 83 is, in turn, affixed to a hub 84 that is journalled within the housing member 72 by means of a ball bearing assembly 85. The hub 84 is connected to the ring gear 83 by means of fasteners or rivets 86. The sprocket 53 has a splined connection to the hub 84 by means of splines 87 so that when the ring gear 83 rotates, the sprocket 53 will be driven. One end of the crankshaft 33 is journalled within the hub 84 by means of anti-friction bearings 88 with an oil seal 89 being disposed at the outer periphery. The opposite end of the crankshaft 33 is rotatably journalled within the cover plate 73 of the housing 32 by means of a further ball bearing assembly 91. A planetary transmission, indicated generally by the reference numeral 92, is provided for establishing a driving relationship between the crankshaft 33 and the ring gear 83, and this connection also includes a one-way clutch 93. This one-way clutch is shown in most detail in Figure 7, and in addition to acting as a one-way clutch, it provides a bearing arrangement for ensuring a coaxial relationship of the various elements of the one-way clutch and thus avoids the necessity of separate bearing elements to maintain the inner and outer races of the one-way clutch in their relationship. Conventionally, the outer element was supported for rotation relative to the inner or driving element by means of roller or ball bearings and thus the bearings and associated pawl elements were all separate components that had to be assembled and added not only to the cost, but the size of the assembly. Such a prior art type of one-way clutch and bearing assembly is shown in Figures 10 and 11 wherein there is provided a driving connection between an inner hub 211 and an outer member such as a sprocket 212. The inner hub 211 has affixed for rotation with it an inner member 213 that pivotally supports a plurality of pawls 214 in pockets 215. These pawls 214 are normally biased outwardly by spring arrangement into receptive recesses 216 formed integrally within the interior of the sprocket 212 so as to establish a driving relationship in the counterclockwise direction as seen in Figure 2 but to permit the sprocket 212 to overrun the hub 211 under some conditions. Ball bearings 217 are interposed in races formed between the hub 211 and a threaded end piece 218 and in the sprocket 212. As a result, it is necessary to provide a complicated assembly arrangement for maintaining the desired relative rotational axes between the hub 211 and sprocket 212 which adds significantly to the cost and complexity of the assembly. Because of the construction which will be described, it will be seen that the necessity for separate bearings is avoided with the one-way clutch mechanism, which is indicated generally by the reference numeral 93 in Figures 6 and 7. This one-way clutch assembly 93 includes a first or inner element 94 which is formed with female splines so as to receive male splines 95 of the crankshaft 33 so as to form a driving connection between the crankshaft 33 and the first element 94. The first element 94 is provided with curved pockets 96 that receive the complementary curved cylindrical portions 97 of pawl elements, indicated generally by the reference numeral 98. These pawl elements 98 have bifurcated fingers 99 which are formed with slots 101 that are aligned with a corresponding slot 102 formed in the outer periphery of the element 94. A retainer spring element 103 is received in these slots 102 and 101 and retains the pawl elements 98 in their positions. The shape of the slots 101 is such that the spring element 103 biases the pawls 98 to an engaged position as shown in Figures 7 and 9. The one-way clutch 93 includes a second or outer member, indicated generally by the reference numeral 104, which is provided with a plurality of recesses 105 that are adapted to receive the pawls 98 and to form a driving relationship between the crankshaft 33 and the second member 104. These pawl-receiving recesses 105 are formed, however, in such a way as to permit the second member 104 to drive or rotate faster than the one-way clutch 94 for a coasting operation or when pedaling backwards. The area between the wedging recesses 105 defines a segmental cylindrical surface 106. This surface is engaged by a corresponding segmental cylindrical surface 107 formed by the member 94 by outstanding portions that extend beyond recesses formed by first and second portions 108 and 109 in which the pawls 98 are received on opposite sides of the pockets 96. Because of the extent of the cylindrical segments or surfaces 107 and 106, there is always full bearing arrangement, albeit less than 360°, around the periphery of the members 94 and 104. Thus the need for separate bearings for providing this relative support are avoided, and the overall construction is thus simplified. As may be seen in Figure 6, the outer one-way clutch 104 carries a plurality of carrier pins 111 on which planet gears 112 are rotatably journalled. These planet gears 112 engage internal gears of a orbital member 113 which is fixed by the fasteners or rivets 86 for rotation with the ring gear 83. It should be noted that the orbit member 113 has a larger diameter where its internal teeth are formed that are engaged with the planet gears 112 then adjacent the end of the pinion shaft 77 as clearly shown in this figure to maintain a relatively small outer diameter for the entire assembly so that the casing assembly 32 has a smaller diameter than that of the crank arms 34. The planet gears 112 are engaged with a sun gear 114 formed by a flange 115 that is affixed axially to the crankshaft 33 but rotatable relative to it. As a result, the planetary transmission 92 formed by the sun gear 114, planet gears 112 and orbit ring gear or member 113, provide a speed reduction between the crankshaft 33 and the sprocket 53 upon pedal operation so as to provide a force amplification. The sun gear 114 acts primarily as a part of the torque sensor previously indicated in block form in Figure 3 and identified by the reference numeral 59 and identified by this same reference numeral in Figures 4 and 6. This torque sensor 59 includes an abutment element 116 that is affixed to a lug 117 formed on the flange 115. This abutment element 116 is engaged with a lever 118 that is affixed to a shaft 119 journalled in the housing member 72 on a pair of anti-friction bearings 121. The shaft 119 is connected to a wiper of a potentiometer 122 so as to provide an electrical output signal indicative of the degree of rotation of the sun gear 114 and, accordingly, the torque exerted by the operator on the pedal assembly. A damper member 123 is engaged by a spring 124 which bears against a plate 125 so as to provide a biasing assembly 126 that acts to hold the lever 118 against rotation, and thus provides the torque measurement. An adjustable stop 127 limits the degree of rotation of the lever 118 and sun gear 114 in the clockwise direction as shown in Figure 4. This type of torque sensor is described also in the aforenoted copending applications. An electrical conduit 128 conveys the signal from the torque sensor 59 and specifically the potentiometer 122 to the controller 47. The speed sensor 58, shown in block form in Figure 3, is comprised of a magnetic element and associated coil that is mounted in the housing piece 72 in proximity to the teeth of the ring gear 83. Hence, upon rotation of the ring gear 83 and sprocket 53, a pulse signal will be transmitted from the speed sensor 58 through a conductor 129 to the controller 46 so as to provide the speed signal required for its control. A small cover piece 131 is affixed to a side of the cover plate 73 by threaded fasteners 132 to protect the various elements and to provide a neat overall assembly. The housing member 72 is provided with a plurality of bossed openings 133 that receive fasteners so as to affix the drive assemble to the frame assembly 22 and specifically the bracket 28 thereof. The construction of the battery case 45 and the way in which the seat 31 may be moved to access the batteries 44 will now be described by particular reference to Figure 12. As has been previously noted, the battery case 45 is positioned to the rear of the seat pillar 29 and is also disposed forwardly relative to the rear wheel 36. The battery case 45 is relatively narrow and is contained laterally between a pair of auxiliary seat tubes 134 that are connected to and form a part of the frame assembly 22 to the rear of the seat pillar 29. A battery case socket 135 is fixed relative to the frame assembly 22 and contains a pair of male electrical connectors 136 that are cooperatively engaged with a female socket 137 carried by the battery case 45 when assembled into the socket 135 so as to complete the electrical connection as aforenoted. A lock mechanism, indicated generally by the reference numeral 138 is provided which has a latching finger 139 that retains the battery case 45 in position and is connected by means of a wire shown schematically at 141 to the main switch 47 so as to be disengaged when a key of the main switch 47 is turned to the lock releasing direction, counterclockwise as viewed in Figure 1. Thus, the batteries 44 cannot be removed unless the operator inserts a key in the main switch 47 and rotates it in the aforenoted direction for release purposes. The battery socket 135 is resiliently mounted on the frame bracket 28 by means of resilient supports 142. As may be seen in Figure 1, when the seat 31 is lowered, the battery case 45 is, in major part, precluded from removal or accessing by the seat 31. A seat adjusting and access assembly, indicated generally by the reference numeral 143, is provided for permitting vertical adjustment in the position of the seat 34 and also to permit the seat 34 to be pivoted in a forward direction from the phantom line view as shown in Figure 12 to an access or service position for removal of the battery case 45 and removal of the batteries 44. This mechanism will now be described by continued reference to Figure 12 although certain of the components are also shown in Figure 1. The seat 31 is affixed by means of a clamping bracket assembly 144 in a known manner to the upper end of a support tube 145. The support tube 145 is slidably supported for movement along an axis defined by the seat pillar 29 and is locked in adjusted position by means of a split type clamp 146 in a known manner. Unlike prior art constructions, however, the support tube 145 has a bracket 147 affixed to its lower end which is, in turn, pivotally connected by means of a pivot pin 148 to a somewhat larger bracket 149 which is captured within the seat pillar tube 29. Hence, when the clamping bracket 146 is released, the mechanism may be slid upwardly to the position shown in solid lines in Figure 12 wherein the member 149 is at the upper end of the seat pillar tube 29. Pivotal movement of the seat 31 and its supporting post 145 about the pivot pin 148 is then possible so as to clear the battery case 45 and permit its removal in a manner which is believed to be obvious from this figure. It should be readily apparent from the foregoing description that the described construction provides a very compact battery and electric motor assist arrangement for a bicycle that maintains a low and balanced center of gravity relative to the axis of the crank shaft 33 without significantly affected ground clearance. In addition, the battery can be readily accessed but is protected against theft or unwanted intrusion.

Claims: An electrically power assisted bicycle (21) comprising a frame (22), a front wheel (24) to be dirigibly supported by said frame (22), a rear wheel (36) journalled for rotation by said frame (22), a seat (31) carried by said frame (22) for accommodating a rider, a pedal assembly journalled by the frame (22) for rotation about a transverse crank axis for operation by the rider seated on said seat (31), a drive means coupling said pedal assembly to said rear wheel (36) for manually driving said rear wheel (36), and an electrical power assist mechanism for transmitting a driving force to said rear wheel (36) through said drive means and comprising an electrical motor (43) and an electrical battery (44) for providing electrical power to said electrical motor (43), characterized in that said electrical motor (43) and said electrical battery (44) are disposed substantially weight-balanced with respect to the crank axis. A bicycle as claimed in claim 1, characterized in that in view of a normal forward traveling direction of the bicycle the electrical motor (43) is disposed in an area in front of the crank axis while the electrical battery (44) is disposed in an area in the rear of the crank axis. A bicycle as claimed in claims 1 and 2, characterized in that both the electrical motor (43) and the electrical battery (44) are disposed substantially in compliance with a vertical longitudinal plane containing the front and rear wheels when the dirigible front wheel is in its straightforward position. A bicycle as claimed in at least one of the preceding claims 1 to 3, characterized in that the electrical motor (43) is disposed below in the substantially parallel to an inclined front main frame tube (27) of the frame. A bicycle as claimed in at least one of the preceding claims 1 to 4, characterized in that the electrical motor (43) is disposed with its output shaft (63) extending at an inclined angle to both the vertical and horizontal and extending in an upward direction from the crank axis and forwardly thereof. A bicycle as claimed in claim 4 or 5, characterized in that the electrical motor (43) is disposed forwardly of the crank axis and is supported beneath the front main frame member (27) and has its output shaft extending generally parallel to and beneath that main frame member (27). A bicycle as claimed in at least one of the preceding claims 1 to 6, characterized in that the electrical battery (44) is disposed in a generally upstanding direction to the rear of the crank axis and beneath the seat. A bicycle as claimed in claim 7, characterized in that the electrical battery (44) is disposed at an inclined angle to the vertical and to the horizontal. A bicycle as claimed in at least one of the preceding claims 1 to 8, characterized in that the frame comprises a head pipe (23) dirigibly supporting the front wheel (24) and the main frame member (27) extending rearwardly and downwardly therefrom to a point adjacent to the crank axis and a seat pillar (29) extending upwardly and rearwardly from a point adjacent to the crank axis and supporting the seat. A bicycle as claimed in at least one of the preceding claims 1 to 9, characterized in that the electrical battery (44) is disposed to the rear and generally parallel to the seat pillar (29). A bicycle as claimed in at least one of the preceding claims 1 to 10, characterized in that the electrical battery (44) is disposed beneath the seat (31) and that means are provided for permitting a movement of said seat for accessing said electrical battery (44). A bicycle as claimed in at least one of the preceding claims 1 to 11, characterized in that a pair of auxiliary seat tubes disposed to the rear of the seat pillar (29) and to the rear end on opposite sides of the electrical battery (44). A bicycle as claimed in at t least one of the preceding claims 1 to 12, characterized in that the electrical battery (44) being received in a battery case (45) disposed beneath the seat (31) and extending generally in parallel to the inclined seat pillar (29). A bicycle as claimed in at least one of the preceding claims 1 to 13, characterized in that the seat (31) is movably supported relative to the seat pillar (29) for accessing the battery case (45) and for accessing said electrical battery (44). A bicycle as claimed in claim 13 or 14, characterized in that the seat (31) supported on the seat pillar (29) by a first portion slidably supported relative to the seat pillar (29) and a second portion also slidably received in the seat pillar (29) and pivotally connected to the first portion for telescopic movement of the first and second portions and pivotal movement of the first portion relative to the second portion. A bicycle as claimed in at least one of the preceding claims 1 to 15, characterized in that planetary gear and roller type transmission are disposed between an output shaft (63) of the electrical motor (43) and a crank shaft (33) of the bicycle drive means. A bicycle as claimed in at least one of the preceding claims 1 to 16, characterized in that said frame (22) which is comprised substantially solely of a head pipe (23), a down pipe (27) extending downwardly and rearwardly from said head pipe (23), and a seat pipe (29) extending generally vertically upwardly from a rear portion of said down pipe (27), the front wheel (24) is dirigibly supported by said head pipe (23), the rear wheel (36) is journalled for rotation by said frame (22), the seat (31) is carried by said seat pipe (29) for accommodating a rider, the pedal assembly (34,35) is journalled by said frame (22) for rotation about a transverse crank axis for operation by a rider seated on said seat (31) contiguous to the juncture of said down pipe and said seat pipe (27), the drive couples said pedal assembly (34,35) to said rear wheel (36) for manual driving of said rear wheel (36), and that the electric power assist mechanism for transmitting a driving force to said rear wheel (36) through said drive comprises the electrical motor (43) disposed longitudinally along one of said pipes (23,27) and entirely on one side of said crank axis, and the battery (44) for providing the only source of electrical power to said electric motor (43) and disposed longitudinally along the other of said pipes (27) entirely on the other side of said crank axis. A bicycle according to claim 1, wherein said human drive means and said electric power assist mechanism are disposed in parallel to each other and an output of said electric power assist mechanism is controlled by a controller (46) in accordance with changes in human powered pedal force, wherein further said frame (22) comprises a head pipe (23), a down tube or mainframe tube (27) extending downward from said head pipe (23) toward the rear and a seat pillar (29) fixed at the rear of said down tube (27), extending upward and fitted with said seat (31) at the top end thereof, so as to form a clearance for leg passage open upward and in the shape of approximately a letter V in profile; on the same shaft line as that of a crankshaft (33) located downward of the bottom of said clearance for leg passage is provided a cylindrical output shaft connected to a rear wheel drive means, said human drive means and said electric drive power assist mechanism being connected to said cylindrical output shaft through one-way clutches (54,57), respectively; and said electric motor (43), said battery unit (45) and said controller (46) are arranged upward from said crankshaft (33) along the outer surfaces of said down tube (27) and said seat pillar (29), with said crankshaft (33) centered and located vertically in the lowest position, so as to take the shape of approximately a letter of V in profile, to be aligned approximately in a row in plan view and to be approximately in parallel to the shaft lines of said down tube (27) and said seat pillar (29), respectively, in the longitudinal direction. A bicycle according to claim 18, wherein members disposed on the down tube side and the down tube (27) in the electric drive system components comprised of the electric motor (43), the battery unit (45) and the controller (46) are enclosed with a cover (48) as an appearance member. A bicycle according to claim 18, wherein the electric motor (43) and the controller (46) are disposed on the underside of the down tube (27), and the battery unit (45) on the rear side of the seat pillar (29).

Inventors: AKITA HISATOSHI, SUZUKI MASAHIRO, TAKATA NOZOMU, AKITA, HISATOSHI, SUZUKI, MASAHIRO, TAKATA, NOZOMU, AKITA, HISATOSHI, C/O YAMAHA HATSUKOKI K. K., SUZUKI, MASAHIRO, C/O YAMAHA HATSUKOKI K. K., TAKATA, NOZOMU, C/O YAMAHA HATSUKOKI K. K.
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1994
Main classification: B62M23
IPC codes: H01M2, B60K1, B62M6